This invention relates to atomizing pump dispensers in general, and more particularly to an improved triple seal valve member particularly useful in a pre-pressurized type atomizing pump dispenser.
With the advent of restrictions against the use of fluorocarbons in atomizing dispensers and the concern for the effects of fluorocarbons on the ozone layer, the development of pumps which can atomize with the type of fine spray previously obtainable only with a pressurized container has become increasingly important.
The most common proposal for providing good atomizing in a pump comprises carrying out some type of a pre-pressurization. A number of different pre-pressurized pumps have been developed which include an outlet valve arrangement which does not operate until a certain amount of pressure builds up in a pump chamber so that a fine atomization without dribble can be accomplished. Typical of such pumps are the pumps described in U.S. Pat. No. 4,025,046; U.S. Pat. No. 3,399,836; U.S. Pat. No. 4,089,442 and French Pat. No. 2,249,716.
Each of the pumps disclosed in the aforementioned patents and patent applications include a pump chamber in which there is disposed, for reciprocal motion, a piston having a stem integral therewith. The piston contains a central axial bore at the inner end of which there is disposed a valve member which maintains an inlet port to that bore closed until pressure builds up in the pump chamber due to an inward depression of the pump stem. Each of the pumps also includes biasing means, typically a spring, which holds the valve member against the port until a sufficient differential pressure builds up to move it away from the inlet port. All of these pumps also include valving means at the inlet to the pump chamber. The purpose of the valving means is to permit refilling of the pump during an outward stroke, but to prevent backflow of the material from the pump chamber during a dispensing stroke. The most common manner of achieving the inlet valve is by means of a check valve. Thus, Pechstein, in U.S. Pat. No. 3,399,836, utilizes a ball check valve for this purpose. In French Pat. No. 2,249,716, the check valve is in the form of a rubber gasket disposed about an extension of the valve member and retained by a plastic cover. When the pump is operated, the pressure developed therein slides the gasket on the stem inward sealing against an opening at the inner end of the pump chamber. After dispensing, the pressure differential, due to the partial vacuum which is drawn inside the pump chamber, results in the gasket being moved upward to open a path for refilling.
In U.S. Pat. No. 4,089,442, a different type of check valve is utilized. The valve member which seals against the inlet port in the dispensing stem has a hollow portion which extends through a throat at the inner end of the pump chamber. Within this hollow section, a spring is disposed and the hollow section is placed in communication with the container. The hollow section is of a larger diameter than the rest of the valve member, being narrowed down at a point below the inlet port into the dispensing stem. This permits openings to be formed from the hollow side of the valve member. When pressure is developed in the chamber, it is pushed inward closing off the openings. When a differential pressure exists, it is pushed upward to permit fluid to flow through the hollow portion of the valve member, the openings and into the chamber. Another device using a conventional ball check is that of U.S. Pat. No. 4,051,983. In the embodiment disclosed therein, what is herein referred to as the valve member and which both acts to seal at the inner end of the pump chamber and to seal off the inlet port to the dispensing stem, is made of three pieces. There is an upper portion which extends into an opening in the piston and dispensing stem assembly to form, with the inlet port to the dispensing stem, a valve. This part has a hollow portion at its inner end. The hollow portion has a plurality of openings formed therein, and retains a ball. To hold the ball in place a third part is inserted into the hollow portion forming an extension of the valve member. This part carries out the necessary sealing at the inner end of the pump chamber.
The aforementioned U.S. Pat. No. 4,025,046, particularly in the embodiment shown in FIG. 4, dispense without the need for a separate inlet valve, using instead cooperation between the valve member and a throat formed at the inner end of the pump chamber. The valve member is constructed so that when the pump is in its at-rest position with the valve member, piston and dispensing stem all fully outward, the valve member, either by means of appropriate channels, tapering or sizing, opens up a path of communication between the container and the pump chamber. This was first disclosed and claimed in U.S. Pat. No. 4,113,145, granted to Philip Meshberg on Sept. 12, 1978, being an improvement on his earlier U.S. Pat. No. 3,211,346 granted Oct. 12, 1965.
Although this principle works quite well in most instances, particularly where the pump chambers are relatively small, or where a measured does is required, there are situations where it does not operate as well as might be desired. Most importantly, if the operator does not allow the stem to return to its fully outward position, i.e., where he executes short strokes, the inlet valve to the pump chamber will not open to allow it to refill. It must be noted that with such an arrangement the inlet to the pump chamber is not opened until the piston has almost reached its at-rest position. On the other hand, when using a conventional check valve, the pump chamber begins refilling almost immediately upon the beginning of the outward stroke. This allows short strokes. A problem can also occur if the operator, instead of releasing the dispensing stem all at once, lets it slowly come out. This permits leakage of air around the piston and improper refilling. Thus, despite the economic advantages of eliminating the need for a separate check valve, there are instances where the inclusion of a check valve is desirable. In particular, a ball check valve which is a proven type of check valve and has been used extensively is desirable. But, where a measured dose is required, of course, the full stroke is needed and a pump of the type disclosed is still preferred. Ideally the construction of such an arrangement should be such as to minimize additional cost. In other words, it is desirable to make such an arrangement with as few pieces as possible. It is also desirable that as many parts of a pump with and without a check valve be identical so that either pump can be supplied to a user with a minimum of effort.